The invention concerns an electrode arrangement having an electrode line which has a closed casing for sealing off its interior relative to the surrounding area and, at its distal end, an electrically conducting surface regions serving as electrodes, as well as fixing means for anchoring the distal end in a body tissue, in particular heart tissue, wherein the fixing means are adapted to be separable from the rest of the electrode line in such a way that the rest of the electrode line is also closed at its distal end when the fixing means are separated off so that the interior of the electrode line is sealed off relative to the surrounding area even when the fixing element is separated off.
Electrode arrangements of this kind are known, for example from DE 30 20 586. Besides the specified electrode arrangements with tines, small barb-like prongs at the outermost distal end of the electrode line, electrode lines with screwing-in tips are also known. The described fixing means serve to anchor the distal end of the electrode line in the cardiac tissue in order to hold it in a defined position and to maintain constant stimulation conditions as far as possible.
An electrode line is introduced, for example, by way of a vein into an atrium or a ventricle of a human heart. In some cases, an electrode line has to be removed again. This gives rise to problems in which the electrode line is anchored in the cardiac tissue, the myocardium, by means of the described fixing means, because the fixing means grows into the tissue as time passes. This makes it more difficult to remove the cardiac pacemaker electrodes, for example, for the purposes of replacement thereof.
Therefore, electrode lines with fixing means that can be separated off have been proposed, and can be found in U.S. Pat. Nos. 5,383,924, 5,908,447, and above-mentioned DE 30 20 586.
An indication in regard to the removal of an electrode line is afforded when infection has been found to occur in the region of a pacemaker connected to the electrode line or in the region of the electrode line itself. In such situations removal of the electrode line should as far as possible not contribute to spreading the infection. The known electrode lines leave something to be desired in this respect.
Furthermore, after some years, not only do the fixing means grow into the myocardium but the electrode line itself is also enclosed by tissue, for example, where it bears against a vessel wall, for example the vena cava. In such situations, removal of the electrode line should entail a minimum amount of injury and damage to the enclosing tissue.
The object of the invention is to provide an electrode arrangement which is simple to remove and without unnecessary health risks.
In accordance with the invention, this object is attained with an electrode arrangement of the kind set forth herein, which has means for separating off the fixing means adapted to effect separation of the fixing means by virtue of forces acting axially within the electrode line.
The invention is based on the notion of avoiding stresses on the patient which occur due to avoidable movements in the region of the outer casing of the electrode line. Avoidable movements of that kind are, for example, rotation of the electrode line as disclosed in DE 30 20 586 about its longitudinal axis in order to unscrew the electrode line from the fixing means described therein. The aim is also to avoid such loadings which are due to a separating device which is to be pushed over the electrode line, as are described in U.S. Pat. No. 5,383,924. Finally, the aim is to avoid the health risks which arise due to an electrode line which is open at the distal end after separation of the fixing means, as septic fluids in the interior of the electrode line can issue from that open end thereof. Those considerations finally led to the realization that electrode lines which are to be separated from the fixing means solely by longitudinal forces acting in the electrode line satisfy all demands. This concept of the invention embraces two variants of the invention, namely one variant in which purely passive separation of the fixing means from the rest of the electrode line is effected solely by pulling on the electrode line, and another variant in which the separation of fixing means and electrode line is actively implemented or promoted by means which are provided in the electrode line.
An advantageous feature of the electrode line according to the invention provides that after separation from the fixing means the electrode line is of a uniform diameter over its entire length or tapers towards the distal end. That makes it easier to withdraw the electrode lines if they should be enclosed by tissue at any point.
Preferably, the fixing means are connected to the rest of the electrode by way of a desired-separation location in such a way that the connection is separable in the region of the desired-separation location by defined forces which are predetermined by the configuration of the desired-separation location. The definedly predetermined forces cause the fixing means to be released from the rest of the electrode line, preferably under the influence of such forces as can be exerted by the cardiac tissue as a reaction to tensile forces exerted on the electrode in the longitudinal direction of the electrode line. The forces required for separation of the desired-separation location depend on the construction thereof. Influencing parameters in this respect are the geometry of the connection and the nature of the material used. By virtue of variations in those influencing parameters, it is possible for one skilled in the art to design the desired-separation location in such a way that forces which are to be exerted by the cardiac tissue itself are sufficient to separate the fixing means from the remainder of the electrode line. Such a design configuration in respect of the desired-separation location makes it possible on the one hand for the end of the electrode line to be securely anchored and on the other hand for the electrode line to be removed for replacement purposes without damaging the cardiac tissue.
In a prembodiment, the fixing means or the electrode line have a projection in the region of the desired-separation location, which engages into a corresponding recess in the respective other part. Such a latching arrangement for the desired-separation location can easily be designed in such a way that it separates under the influence of defined forces.
An alternative embodiment is distinguished by a releasable mechanical coupling between the fixing means and the rest of the electrode line. An actuating means is brought into engagement with the coupling to release the coupling. In contrast to the above-described alternative embodiment in which the desired-separation location separates passively as a reaction to the influence of defined forces, the connection between the fixing means and the rest of the electrode line, in the case of the last-mentioned alternative embodiment, can be released actively by means of the corresponding actuating means. The advantage of the last-mentioned alternative embodiment is that the forces which act upon replacement of an electrode line in the myocardium can be even less. On the other hand, the higher level of structural expenditure for the electrode line is a counterpart consideration.
In a preferred configuration of the last-mentioned alternative embodiment, the coupling has retaining or detent elements which engage behind a projection on the fixing means and which are to be moved by the actuating means into a position of releasing the projection. A coupling of this nature can be easily constructed with a small number of components, in such a way that it is reliable in operation. A detailed description of such a coupling is to be found herein.
In the case of an electrode arrangement with an electrically conducting surface at its distal end, to serve as a tip electrode, the desired-separation location in a preferred embodiment is of such a nature that the fixing means can be separated from the rest of the electrode line in such a way that upon separation the tip electrode remains on the electrode line.
An alternative is distinguished in that the electrode line has electrical contact elements for contacting the tip electrode, so that the fixing means are separable from the rest of the electrode line in such a way that, upon separation, the tip electrode remains on the fixing means.
The fixing means preferably has marking means which can be located by electromagnetic or acoustic locating means, such as for example an X-ray machine. Such marking means make it possible to locate a fixing means which has remained in the myocardium after the removal of an electrode line and to position an electrode line which is to be re-introduced, so that the fixing means thereof do not penetrate into the cardiac tissue at the same location as the preceding electrode line.
If the fixing means are such tines which are of a barb-like configuration, the marking means are preferably disposed in the tines.
Furthermore, a preferred electrode arrangement is one which is characterized by a synthetic resin material in the region of the desired-separation location, said material being plastic upon connection of the fixing means to the rest of the electrode line. The plastic synthetic resin material preferably contains silicone. The synthetic resin material can selectively or simultaneously perform a sealing and adhesion, that is to say gluing, function. As it is plastic or fluid when the fixing means are connected to the rest of the electrode line, it is suitable for completely filling all gaps which could remain between the fixing means and the rest of the electrode line.
It is to be noted that the features of the invention can also be transferred to those electrode arrangements which, instead of fixing means with so-called tines, have for example screwing-in tips of a corkscrew-type configuration as fixing means and possibly additionally as the electrode. Screwing-in tips of that kind can also be connected to the rest of the electrode line in the manner described hereinbefore and also as described in the specific description.